Phase current detector

Abstract

A first condenser (2a) is connected between output terminals of a rectifier circuit (2) which receives an AC power (1) as an input, and a three phase inverter (3) is connected in parallel with respect to the first condenser (2a), and output of the three phase inverter (3) is supplied to a motor (4), and a second condenser (3a) is connected in parallel to the input side of the three phase inverter (3), and a current detector (5) is connected between the first condenser (2a) and the second condenser (3a), and a third condenser is connected in parallel to the first condenser (2a) at a position slightly power side with respect to the current detector (5), and the capacitance of the second condenser (3a) is determined as small as possible within the range in which power devices are not destroyed by surge voltage due to switching, therefore, ringing is suppressed, and taking of current is performed rapidly and with high accuracy.

Description

technical field [0001] The present invention relates to a phase current detection device that detects a motor based on a current of a DC link and an additional vector diagram in a motor drive device that supplies an output from a PWM inverter to a motor and drives the motor phase current. Background technique [0002] Conventionally, in a motor drive device in which an inverter drives a motor, a device for deforming an output pulse into a measurable output has been proposed as a device for detecting a motor phase current. [0003] When the above-mentioned structure is adopted, the following disadvantages occur, namely, current measurement error due to ringing, waveform distortion due to extension of pulse output time, reduction of operating range, and generation of abnormal noise. [0004] In particular, since no solution for ringing is proposed, there are disadvantages that it is difficult to reduce ringing, high-speed response cannot be performed, or measurement accuracy ...

AI Technical Summary

Problems solved by technology

[0003] When the above structure is adopted, the following disadvantages occur, namely: current measurement error caused by ringing, waveform distortion caused by prolongation of pulse output time, reduction of operating range, generation of abnormal noise, etc.

[0004] In particular, since no solution for ringing is proposed, there are disadvantages that it is difficult to reduce ringing, high-speed response cannot be performed, or measurement accuracy cannot be improved.

[0005] Also, although it is considered that a parallel resistor can be used to detect the pulse current flowing through the DC link, it is difficult to reduce the influence of noise and improve the measurement accuracy, and there is a problem that it cannot be detected for pulses other than long pulses due to the peak voltage caused by the inductance of the parallel resistor. Bad Cases of Current Sensing with Pulse

Therefore, the use of parallel resistors to detect phase currents has not yet reached practicality

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